1. Field of the Invention
The present invention relates to a liquid receiver whose gas-liquid separation function is improved.
2. Description of the Prior Art
In general, a cooling system for automobile has a liquid receiver which receives an excessive quantity of a refrigerant in the cooling cycle, separates gas from liquid and removes water and dust.
A conventional liquid receiver is shown in FIG. 4. A liquid receiver 100A has a tank body 102, the tank body 102 having an upper plate 103 and a lower plate 104 at its upper end and the lower end, respectively. The upper plate 103 is provided with a head portion 105. The tank body 102 is joined to the upper plate 103 and the lower plate 104 and the upper plate 103 is joined to the head portion 105 by proper joining means such as arc welding.
A refrigerant inlet portion 106 and a refrigerant outlet portion 107 are formed in the head portion 105. The refrigerant inlet portion 106 is an L-shaped passage whose an end is communicated with a condenser (omitted from illustration) and another end is communicated with the inner space in the tank body 102. The refrigerant outlet portion 107 is a passage whose an end is communicated with an expansion valve (omitted from illustration) and another end is connected to a refrigerant output pipe 108.
The refrigerant output pipe 108 extends downward until it reaches a position near a bottom 102a of the tank body 102. A sight glass 109 is provided at a position above the refrigerant output pipe 108 for the purpose of looking the inside portion of the refrigerant outlet portion 107.
A desiccant charging portion 110 is secured to an intermediate portion of the refrigerant output pipe 108. The desiccant charging portion 110 has support plates 112 and 113 in which a multiplicity of small apertures are perforated. A desiccant 114 and a filter 115 made of glass wool or the like are held between the support plates 112 and 113. The desiccant 114 acts to absorb water contained in the refrigerant, while the filter 115 acts to remove dust therein.
However, the cylindrical tank body 102 of the liquid receiver 100A is formed by joining the upper plate 103 and the lower plate 104 to the two ends of the cylindrical body by proper joining means such as arc welding. Therefore, it is complicate to manufacture the tank body 102 and the number of the components cannot be reduced, causing disadvantages in terms of the reliability in the airtightness performance and the overall cost to be arisen. As a result, a liquid receiver 100B of a type shown in FIG. 5 has been used recently as disclosed in Japanese Utility Application Laid-Open No. 61-203271.
The liquid receiver 100B comprises the cylindrical tank body 102 with a bottom, and the head portion 105 provided in an upper opening 106 of the tank body 102, the head portion 105 and the tank body 102 being coupled to each other by press-fitting means such as caulking.
As a result, the number of the welding portions and that of the components can be reduced. Furthermore, the assembling work can be easily completed, satisfactory reliability in the airtightness performance can be obtained and the overall cost can be reduced.
However, since the above-described liquid receiver 100B is arranged in such a manner that the desiccant charging portion 110 is disposed in the bottom, the gas-liquid mixed refrigerant, which has moved downwards from the refrigerant inlet portion 106, passes through the desiccant charging portion 110 immediately before it is introduced into the refrigerant output pipe 108. Therefore, if the quantity of the charged refrigerant has been reduced therein, the gas refrigerant can be easily introduced into the refrigerant output pipe 108, causing the gas-liquid mixed refrigerant to easily flow out.
FIG. 6 shows a liquid receiver 100C disclosed in U.S. Pat. No. 4,649,719 and arranged in such a manner that the desiccant charging portion 110 is positioned at an intermediate position of the refrigerant output pipe 108. Therefore, the above-described problem in that the gas and liquid are mixed with each other can be satisfactorily overcome. As a result, the desiccant charging portion 110 exhibits the rectification effect so that the level of the storaged liquid refrigerant cannot be disordered by the refrigerant which has moved downwards. Therefore, a stable liquid level can be obtained.
The liquid receiver shown in FIG. 4 can exhibit the same effect.
However, since the liquid receiver 100C is arranged in such a manner that the tank body 102 is in the form of a cylinder, the capacity of a space below the desiccant charging portion 110 becomes too large. Therefore, a large quantity of the refrigerant must, of course, be enclosed. Furthermore, if the quantity of the refrigerant in the liquid receiver 100C has been reduced, the stable liquid level can be lowered, causing the above-described gas-liquid mixed refrigerant to be introduced into the expansion valve. As a result, the cooling performance can be deteriorated.
Another problem takes place in that it is difficult to assemble the desiccant charging portion 110 of the liquid receiver 100C and it is difficult to adjust the quantity of the desiccant since the upper and the lower support plates 112 and 113 are fastened to the refrigerant output pipe 108 by proper securing means such as welding or brazing. That is, since the desiccant charging portion 110 is arranged in such a manner that the desiccant is held between the upper and the lower support plates 112 and 113 each of which is secured to the refrigerant output pipe 108, the distance between the two support plates 112 and 113 must be adjusted when the quantity of the desiccant is desired to be adjusted. However, it is extremely difficult for the quantity of the desiccant enclosed to be adjusted by the support plates 112 and 113 which are fastened to the refrigerant output pipe 108 by the securing means such as welding or brazing. Furthermore, it is difficult to enclose and secure the desiccant in the tank.
A liquid receiver 100D has been disclosed in Japanese Utility Application Laid-Open No. 53-38052 in which a desiccant 114 is enclosed in the tank body 102 in such a manner that the tank body 102 is, as shown in FIG. 7, divided into two sections and a pan 116 is provided in the lower section of the thus divided tank body 102 so as to enclose the desiccant 114 on the pan 116.
The liquid receiver 100D is manufactured by the steps of disposing a sleeve 117, through which the refrigerant output pipe passes, in the central portion of the above-described pan 116 so as to be then disposed in the tank body 102, and forming the desiccant charging portion 110. Then, the desiccant 114 is enclosed in the desiccant charging portion 110, and the refrigerant output pipe 108 the upper end of which is integrated with the head portion 105 and to which a cap 118 of the desiccant charging portion 110 is fastened via a rubber bush 119 is passed through the sleeve 117. Then, the rubber bush 119 is fitted in the sleeve 117 so that the liquid receiver 100D is manufactured.
However, when the desiccant 114 is enclosed in the liquid receiver 100D, the desiccant 114 can be unconsciously dropped into the tank body 102 through the sleeve 117. It arise a problem in that the grains of the dropped desiccant 114 hinder the smooth flow of the refrigerant or a problem in that the expansion valve disposed in the lower stream to the drying agent 114 can be clogged with the grains of the dropped desiccant 114 during operating the cooling cycle.
The inventors of the present invention have been making studies for the purpose of overcoming the above-described problems. As a result, a fact was found that the level of the liquid refrigerant storaged in the liquid receiver must be maintained stably and at a high level when the performance of separating gas from liquid is desired to be improved. In particular, in the case where the liquid receiver whose basic structure is arranged in such manner that the desiccant charging portion is disposed in the intermediate portion, the level of the liquid refrigerant may be raised by positioning the portion of the tank body below the desiccant charging portion at a position adjacent to the refrigerant output pipe for the purpose of reducing the space around the refrigerant output pipe. Thus, the inventors have achieved the present invention basing upon the above-described knowledge. Furthermore, another advantage can be obtained from the thus structured present invention in that the necessity of using a large quantity of the Freon gas destructing the ozone layers in the atmospheric air, which has been at issue recently, can be eliminated and the quantity of the refrigerant can thereby be saved.